The present invention relates to a brushless DC motor having a step skewed rotor and more particularly to a skewed rotor formed from a plurality of identically shaped bread loaf magnets mounted on a rotor shaft having a portion having a substantially uniform cross sectional configuration.
Permanent magnet motors with skewed rotors are known in the prior art. One known arrangement utilizes a skewed rotor wherein complicated machining is required to produce the individual skewed rotor sections which are mounted on a cylindrical shaft to form the skewed rotor. The non-linearity of the surfaces of each skewed magnet are difficult and costly to machine.
It is also known to utilize shaped magnets to create a step skew on the rotor wherein the rotor shaft is machined differently for different rotor sections to cause the step skew. This results in costly extra machining effort and problems in maintaining the required tight tolerances.
Step skew is also known utilizing a square rotor shaft having a substantially uniform cross sectional area where magnets of different shapes are utilized to affect the step skew. The utilization of different shaped magnets also requires costly extra machining and assembly effort.
From a commercial and manufacturing stand point, it is desirable to minimize the cost and complexity of the skewed rotor construction by utilizing a rotor shaft having a substantially uniform cross sectional area and by utilizing a plurality of bread loaf shaped magnets having a substantially uniform size and shape to construct the stepped skewed rotor.